Mobile machines such as haul trucks, scrapers, wheel loaders, and other types of heavy machinery are used to perform a variety of tasks. During the performance of these tasks, the machines often operate in conjunction with a limited resource, for example a haul road, a loading machine such as an excavator or front shovel, or a processing; machine such as a crusher or screen. When operating in conjunction with a limited resource, operation of a mobile machine relative to the resource and to other mobile machines competing for the same resource should be carefully managed to avoid machine collisions and to increase profit. The need to properly manage the machines can become even more important when the machines are autonomously or semi-autonomously controlled.
Historically, each machine would determine its own position at the worksite, and relay this position to a central computer. The central computer, after receiving a position message from a particular machine, would then confirm receipt of the message with a return message to that machine. The machine sending the original message would then check the returned confirmation message to make sure that the original message had been properly sent and received, and send an additional message if any errors in transmission were detected. When confirmation of the original message is made by both the machine and the central computer, the central computer would update a map at the worksite, and relay the map to the machine that sent the original message for use in controlling the machine. Similar confirmation messages regarding transmission of the map would then be generated. Although adequate for some applications, the number of messages sent between machines and the central computer were excessive and required large transmission bandwidths and computing power at the worksite.
An alternative method for communicating messages is described in U.S. Pat. No. 6,006,159 (the '159 patent) issued to Schmier et al. on Dec. 21, 1999. In particular the '159 patent describes a public transit vehicle arrival information system. The system includes global position determining devices located in different public transportation vehicles for determining the locations of the vehicles along their defined routes. A central computer is coupled to the global position determining devices for receiving the locations of the vehicles therefrom. The computer is programmed to compute and update from the present locations, a transit data table. The transit data table is then made available for public access via pagers, notebooks, computers, and telephones.
Although the system of the '159 patent may be able to receive and transmit location information with a reduced number of messages, it may still be less than optimal. In particular, the system of the '159 patent may be unable to ensure that reliable information is received from and relayed to particular users of the system at a desired frequency. Without this functionality, the system of the '159 patent may not be applicable to fleet operations where machine control can be affected by the information.
The disclosed tracking system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.